The present invention relates to a foam laminate foil or web, which includes a polyolefin foam foil or layer (top layer) (bottom layer), a nonfoam top foil or nonfoam surface layer, containing a mixture or alloy of an elastomer grafted styrene-acrylonitrile copolymers (ASA) in a certain weight proportion, together with an intermediate foil or layer arranged between the polyolefin foam bottom layer and the top layer, the intermediate layer prepared from at least one low pressure polyethylene and an ethylene vinyl ester copolymer or terpolymer.
In German Offenlegungsschrift No. 27 21 532 a process for the preparation of composite foam foils is disclosed, wherein an unfoamed synthetic plastic layer (B) consisting of a 20 .mu.m-5mm thick layer, is applied to a foamed synthetic plastic layer (A) consisting of a 1-120 mm thick foamed plastic web of an ethylene homo- or copolymer and having a density between 10 g/l and 200 g/l. The layers are joined together by means of a compacting pressure, or else the layers (A) and (B) are adhesively joined by the use of a coupling agent coextruded with the unfoamed synthetic plastic layer (B). The synthetic materials for the unfoamed layer (B) are ethylene polymers. Other usable synthetic materials are styrene polymers, such as for example polystyrene, copolymers of styrene with the usual comonomers, such as acrylonitrile, acryl esters or maleic ester anhydride, which may be modified optionally by rubbers based on butadiene or acryl ester polymers; also homo- or copolymers of propylene, methylmethacrylate, vinyl chloride or vinylidene chloride. Thermoplastic polycondensates and polyadducts may also be used, such as for example polyamides, linear polyesters, polyacetates or polycarbonates.
Foam laminate foils, prepared by the process of German Offenlegungsschrift No. 27 21 532, comprise a polyethylene foam, an unfoamed layer or foil of a styrene-acrylonitrile copolymer and an intermediate layer of polyvinylacetate, but pose the risk of delamination at elevated temperatures, and thus the adhesion of the individual layers to each other is inadequate for many applications.
Such delamination is particularly apparent in the 6-36 hour thermal aging test of molded parts at 120.degree. C., by the separation of the top foil as the result of shrinkage phenomena from the polethylene foam. As the layers of th coupling agents in most cases have lower physical properties than the surface foil and the PE foam, they affect the properties of the composite detrimentally if used in the form of a heavier layer.